Knowledge Base

Gigajot's quanta image sensor technology boosts emerging detector imaging capabilities via high-resolution, high-speed, and low-power linear photon counting at room temperature. While CMOS imagers have evolved significantly since the 1960s, photon-counting sensitivity has still required the use of specialized sensors that often come with detrimental drawbacks. This changed recently with the emergence of new quanta image sensor (QIS) technology, which pushes CMOS imaging capabilities to their fundamental limit while also delivering high-resolution, high-speed, and low-power linear photon counting at room temperature. The QIS paradigm envisioned a large array of specialized pixels, called jots, that are able to accurately detect single photons at a very fast frame rate. The technology’s unique combination of high resolution, high sensitivity, and high frame rate enables imaging capabilities that were previously impossible to achieve.


Publication Date: March 2022

Gigajot's Quanta Image Sensors - New Photon Counting Detectors Expand Frontiers in Imaging

Publication Date: January 2022


This paper reports a 4Mpixel, 3D-stacked backside illuminated Quanta Image Sensor (QIS) with 2.2um pixels that can operate simultaneously in photon-counting mode with deep sub-electron read noise (0.3e- rms) and linear integration mode with large full-well capacity (30k e-). A single-exposure dynamic range of 100dB is realized with this dual-mode readout under room temperature. This QIS device uses a cluster-parallel readout architecture to achieve up to 120fps frame rate at 550mW power consumption.

Authors: Jiaju Ma, Dexue Zhang, Omar A. Elgendy, Saleh Masoodian

Publication Date: 19 June 2021


This paper reports a 16.7 Mpixel, 3D-stacked backside illuminated Quanta Image Sensor (QIS) with 1.1 μm-pitch pixels which achieves 0.19 e- rms array read noise and 0.12 e- rms best single-pixel read noise under room temperature operation. The accurate photon-counting capability enables superior imaging performance under ultra-low-light conditions. The sensor supports programmable analog-to-digital convertor (ADC) resolution from 1-14 bits and video frame rates up to 40 fps with 4096 x 4096 resolution and 600 mW power consumption.

Authors: Jiaju Ma, Dexue Zhang, Omar A. Elgendy, Saleh Masoodian

Publication Date: 13 April 2021


Low-light imaging is a challenging task because of the excessive photon shot noise. Color imaging in low-light is even more difficult because one needs to demosaick and denoise simultaneously. Existing demosaicking algorithms are mostly designed for well-illuminated scenarios, which fail to work with low-light. Recognizing the recent development of small pixels and low read noise image sensors, we propose a learning-based joint demosaicking and denoising algorithm for low-light color imaging. Our method combines the classical theory of color filter arrays and modern deep learning. We use an explicit carrier to demodulate the color from the input Bayer pattern image. We integrate trainable filters into the demodulation scheme to improve flexibility. We introduce a guided filtering module to transfer knowledge from the luma channel to the chroma channels, thus offering substantially more reliable denoising. Extensive experiments are performed to evaluate the performance of the proposed method, using both synthetic datasets and real data. Results indicate that the proposed method offers consistently better performance over the current state-of-the-art, across several standard evaluation metrics.

Authors: Omar A. Elgendy, Abhiram Gnanasambandam, Stanley H. Chan, Jiaju Ma

Publication Date: 25 January 2021


Quanta Image Sensor (QIS) provides system-on-chip solutions for a wide range of consumer, scientific, and industrial imaging applications, by utilizing advanced CMOS fabrication technologies [1]. In this paper, the characteristics of the multi-bit QIS are explained, and its excellent low-light imaging capabilities under photonlimited exposure conditions with less than 2 photoelectrons/jot/frame are experimentally demonstrated at room temperature using a Gigajot QIS prototype camera (Figure 1).

Authors: Jiaju Ma, Yu-Wing Chung, Abhiram Gnanasambandam, Stanley H. Chan, Saleh Masoodian

Publication Date: 23 June 2017


Quanta Image Sensor (QIS) is a single-photon detector designed for extremely low light imaging conditions. Majority of the existing QIS prototypes are monochrome based on single-photon avalanche diodes (SPAD). Passive color imaging has not been demonstrated with single-photon detectors due to the intrinsic difficulty of shrinking the pixel size and increasing the spatial resolution while maintaining acceptable intra-pixel cross-talk. In this paper, we present image reconstruction of the first color QIS with a resolution of 1024 × 1024 pixels, supporting both single-bit and multi-bit photon counting capability. Our color image reconstruction is enabled by a customized joint demosaicing-denoising algorithm, leveraging truncated Poisson statistics andvariance stabilizing transforms. Experimental results of the new sensor and algorithm demonstrate superior color imaging performance for very low-light conditions with a mean exposure of as low as a few photons per pixel in both real and simulated images.

Authors: Abhiram Gnanasambandam, Omar Elgendy, Jiaju Ma, Stanley H. Chan

Publication Date: 10 June 2019


In several emerging fields of study such as encryption in optical communications, determination of the number of photons in an optical pulse is of great importance. Typically, such photon-number-resolving sensors require operation at very low temperature (e.g., 4 K for superconducting-based detectors) and are limited to low pixel count (e.g., hundreds). In this paper, a CMOS-based photon-counting image sensor is presented with photon-number-resolving capability that operates at room temperature with resolution of 1 megapixel. Termed a quanta image sensor, the device is implemented in a commercial stacked (3D) backside-illuminated CMOS image sensor process. Without the use of avalanche multiplication, the 1.1 μm pixel-pitch device achieves 0.21e− rms0.21e− rms average read noise with average dark count rate per pixel less than 0.2e−/s0.2e−/s, and 1040 fps readout rate. This novel platform technology fits the needs of high-speed, high-resolution, and accurate photon-counting imaging for scientific, space, security, and low-light imaging as well as a broader range of other applications.

Authors: Jiaju Ma, Saleh Masoodian, Dakota A. Starkey, Eric R. Fossum

Publication Date: 20 December 2017


Characterization of quanta image sensor pixels with deep sub-electron read noise is reported. Pixels with conversion gain of 423μV /e- and read noise as low as 0.22e- r.m.s. were measured. Dark current is 0.1e-/s at room temperature, and lag less than 0.1e-. This is one of the first works reporting detailed characterization of image sensor pixels with mean signals from sub-electron (0.25e-) to a few electrons level. Such pixels in a nearly-conventional CMOS image sensor process will allow realization of photon-counting image sensors for a variety of applications.

Authors: Jiaju Ma, Dakota Starkey, Arun Rao, Kofi Odame, Eric R. Fossum

Publication Date: 22 September 2015


The first quanta image sensor jot with photon counting capability is demonstrated. The low-voltage device demonstrates less than 0.3e- r.m.s. read noise on a single read out without the use of avalanche gain and single-electron signal quantization is observed. A new method for determining read noise and conversion gain is also introduced.

Authors: Jiaju Ma, Eric R. Fossum

Publication Date: 13 July 2015


This paper presents a pathfinder binary image sensor for exploring low-power dissipation needed for future implementation of gigajot single-bit quanta image sensor (QIS) devices. Using a charge-transfer amplifier design in the readout signal chain and pseudostatic clock gating units for row and column addressing, the 1-Mpixel binary image sensor operating at 1000 frames/s dissipates only 20-mW total power consumption, including I/O pads. The gain and analog-to-digital converter stages together dissipate 2.5 pJ/b, successfully paving the way for future gigajot QIS sensor designs.

Authors: Saleh Masoodian, Arun Rao, Jiaju Ma, Kofi Odame, Eric R. Fossum

Publication Date: 29 July 2015


A new photodetector designed for Quanta image sensor application is proposed. The photodetector is a backside-illuminated, buried photodiode with a vertically integrated pump and transfer gate and a distal floating diffusion to reduce parasitic capacitance. The structure features compact layout and high conversion gain. The proposed device is modeled and simulated, and its performance characteristics estimated.

Authors: Jiaju Ma, Eric R. Fossum

Publication Date: 12 January 2015


The Quanta Image Sensor (QIS) was conceived when contemplating shrinking pixel sizes and storage capacities, and the steady increase in digital processing power. In the single-bit QIS, the output of each field is a binary bit plane, where each bit represents the presence or absence of at least one photoelectron in a photodetector. A series of bit planes is generated through high-speed readout, and a kernel or “cubicle” of bits (x, y, t) is used to create a single output image pixel. The size of the cubicle can be adjusted post-acquisition to optimize image quality. The specialized sub-diffraction-limit photodetectors in the QIS are referred to as “jots” and a QIS may have a gigajot or more, read out at 1000 fps, for a data rate exceeding 1 Tb/s. Basically, we are trying to count photons as they arrive at the sensor. This paper reviews the QIS concept and its imaging characteristics. Recent progress towards realizing the QIS for commercial and scientific purposes is discussed. This includes implementation of a pump-gate jot device in a 65 nm CIS BSI process yielding read noise as low as 0.22 e− r.m.s. and conversion gain as high as 420 µV/e−, power efficient readout electronics, currently as low as 0.4 pJ/b in the same process, creating high dynamic range images from jot data, and understanding the imaging characteristics of single-bit and multi-bit QIS devices. The QIS represents a possible major paradigm shift in image capture.

Authors: Eric R. Fossum, Jiaju Ma, Saleh Masoodian, Leo Anzagira, Rachel Zizza

Publication Date: 10 August 2016